1. Field of the Invention
The present invention relates to a connecting and retaining device for a linear mechanism using rollers as rolling elements, wherein the special design of the spacer portion is suitable for integral formation and fast mass production, and can prevent skew position, friction and impact of the rollers, ensuring a stable transmission.
2. Description of the Prior Art
Since linear transmission products are being applied more and more widely in the modern industry, various linear transmission mechanisms have widely come into human life, manufacturing factory and high science and technology instruments, such as linear guideway, ball screw, and the like. Particularly in a large-scale precision mechanism are usually installed various large and small ball screws or linear guideway systems. Although the technology for linear transmission element is developing fast, consumers still need the technology to be improved uninterruptedly. Therefore, there are still some problems to be solved. And this desire for constant improvement of technology is particular strong in many high precision mechanism-manufacturing fields (such as wafer process equipment, CNC equipment, etc) that require comparative stability and quiet. Hence, the existing linear mechanism still has some technological blind spots to be improved.
The designs of the existing roller spacer of a linear guideway currently on the market generally include the following three types:    A. a first conventional roller spacer as shown in FIG. 1, in which, a chain 12 is connected at either end surface to the respective rollers 10, and the spacer portion 11 of the chain 12 is made by using the rollers 10 as a core of the mold. The rollers 10 are initially placed in the male and the female molds, and then the plastic is injected along the surface of the rollers 10. This type roller spacer has the following disadvantages (U.S. Pat. No. 6,626,572 B2):    1, the spacer portion 11 of the chain 12 is formed directly between the rollers 10 by using the rollers 12 as mold core, the related production technology is very complicated. Furthermore, the size of the mold has to change according to different sizes. When the chain 12 is comparatively long, the number of to-be-implanted rollers 10 will be relative large, the production time will be long and production complexity will be increased, and the resultant technical cost will be relatively high.    2, the spacer portion 11 of the chain 12 is formed directly between the rollers 10 by using the rollers 10 as mold core, it must apply release agent between the spacer portion 11 and the rollers 10 prior to the formation of the spacer portion 11, this also makes the production process more complicated and increases the production cost.    3, the spacer portion 11 of the chain 12 is formed with two concave side surfaces for mating with the rollers 10, and the concave side surfaces of the spacer portion 11 has the same radius of curvature as the rollers 10. As a result, the spacer portion 11 comes into a surface contact with the rollers 10, substantially increasing the friction resistance between the rollers and the spacer portion.    B. Another conventional embodiment is shown in FIG. 2, likewise, the rollers 10 are also used as a mold core, and then the spacer portion 13 is formed by injecting plastic directly on and between the surfaces of the rollers 10. Each of the spacer portions 13 is formed with a protruding connecting portion 131 (as disclosed in U.S. Pat. No. 6,390,678 B1) for cooperating with the rollers 10. This design is similar with the production technology of the first conventional product, and the difference between the two is the location of the protruding connecting portion 131. This conventional spacer also has the following disadvantages:    1, the spacer portion 13 of the protruding connecting portion 131 is formed directly between the rollers 10 by using the rollers 10 as mold core, the related production technology is very complicated. Furthermore, the size of the mold has to change according to different sizes (when the size is comparatively long, the mold will become large), the production complexity will be increased, and the resultant production cost will be relatively high.    2, the spacer portion 13 is formed directly between the rollers 10 by using the rollers 10 as mold core, it must apply release agent between the spacer portion 13 and the rollers 10 prior to the formation of the spacer portion 13, this also makes the production process more complicated and increases the production cost.    3, the protruding connecting portion 131 of the second conventional embodiment is located at the center of the side contacting the rolling surface of the rollers, accordingly, a special guiding groove must be made in the ball rolling groove of the sliding block for accommodation of the protruding connecting portion 131. Since making such a guiding groove is not easy, the production cost of this second conventional embodiment will still be high, moreover, the protruding connecting portion 131 may interfere with the rolling motion of the rollers.    4, the spacer portion 13 of this second conventional embodiment is also formed with two concave side surfaces for mating with the rollers 10, and the concave side surfaces of the spacer portion 13 has the same radius of curvature as the rollers 10. As a result, the spacer portion 13 will have a complete surface contact with the rollers 10, substantially increasing the friction resistance between the rollers and the spacer portion.    5, the radial direction of the rollers 10 is the most important loading direction, and the protruding connecting portion 131 of the second conventional embodiment is exactly located in the radial direction of the rollers 10, such arrangement will considerably reduce the rolling contact area of the rollers with respect to the groove of the sliding block, and as a result, the load capacity and the rigidity of the liner guideway will be substantially reduced.    C. Finally, please refer to FIG. 3, a third conventional embodiment is illustrated, wherein two connecting portion 15 is disposed at the contacting edge on both end surfaces of the rollers 10, and a plurality of slant supporting portions 14 obliquely extend inward. The slant supporting portions 14 are oppositely arranged in pairs and a spacer portion 16 is connected between each paired slant supporting portions 14. The spacer portion 16 is adapted to abut against the rolling surface of the rollers 10 (as disclosed in U.S. Pat. No. 2005/0152625 A1). This design also has the following disadvantages:    1, the two connecting portions 15 are mounted at the contacting edge on both end surfaces of the rollers 10, and the connecting portions 15 are flush with the connecting portion of the rollers 10, therefore, the connecting portions 15 of this third conventional embodiment will interfere with the contacting portion of the rolling surfaces at both sides of the rollers 10, and will create a resistance to the rolling of the rollers 10 (it is likely to form a contact friction).    2, furthermore, the slant supporting portions 14 of the third conventional embodiment are of obliquely extending type, the relatively short spacer portion 16 will only contact the mid portion of the rollers 10. Since the rollers 10 are only subjected to a retaining force from a single side, the spacer portion 16 will be likely to sway with the cooperation of the slant supporting portions 14, this only will cause the operation to be unstable.
It is understood from the conventional products described above that the roller system of the linear mechanism is still unable to maintain a stable operation. To solve the aforementioned problems, the inventor of this invention, on the basis of the accumulated experience and skills associated with the linear transmission field, develops a brand new roller connecting and retaining device that is a unitary structure suitable for mass production and can prevent the problems of the rollers, such as slant position, friction, impact and skip, ensuring that the linear guideway can operate smoothly.